I. Field of the Invention
The present invention relates generally to wireless communication systems, and more specifically, to a repeater for use in wireless communication systems having an embedded wireless communication device capable of interacting with base stations communicating with and through the repeater to affect control of repeater gain and output power.
II. Related Art
Wireless communication systems have developed a great deal in recent years and enjoy widespread use. There are presently many different types of wireless communication systems in use, including Cellular and Personal Communications Service (PCS) systems. Examples of known cellular systems include the cellular Analog Advanced Mobile Phone System (AMPS), and digital cellular systems based on Code Division Multiple Access (CDMA), Time Division Multiple Access (TDMA), the Global System for Mobile access (GSM) variation of TDMA, and newer hybrid digital communication systems using both TDMA and CDMA technologies.
The use of CDMA techniques in a multiple access communication system is disclosed in U.S. Pat. No. 4,901,307, entitled “Spread Spectrum Multiple Access Communication System Using Satellite Or Terrestrial Repeaters” and U.S. Pat. No. 5,103,459, entitled “System And Method For Generating Signal Waveforms In A CDMA Cellular Telephone System,” both of which are assigned to the assignee of the present invention and are incorporated herein by reference.
The method for providing CDMA mobile communications was standardized in the United States by the Telecommunications Industry Association/Electronic Industries Association in TIA/EIA/IS-95-A entitled “Mobile Station-Base Station Compatibility Standard for Dual-Mode Wideband Spread Spectrum Cellular System,” referred to herein as IS-95. Combined AMPS & CDMA systems are described in TIA/EIA Standard IS-98. Other communications systems are described in the IMT-2000/UM, or International Mobile Telecommunications System 2000/Universal Mobile Telecommunications System, standards covering what are referred to as wideband CDMA (WCDMA), cdma2000 (such as CDMA2000 1x or 3x standards, for example) or TD-SCDMA.
In wireless communication systems mobile stations or user terminals receive signals from fixed position base stations (also referred to as cell cites or cells) that support communication links or service within particular geographic regions adjacent to or surrounding the base stations. In order to aid in providing coverage, each cell is often sub-divided into multiple sectors, each corresponding to a smaller service area or geographic region. An array or series of base stations placed adjacent to each other form a communication system capable of servicing a number of system users, over a larger region.
Unfortunately, as extensive as the total coverage areas of many wireless systems appear to be, providing service or coverage to many mobile stations is not without difficulties. The deployment or positioning of base stations within a system may leave “gaps” or “holes” in the coverage area. That is, the arrangement of the base stations, which can be dictated by various known system design criteria, economics, convenience, or local zoning restrictions, does not allow the signal coverage of some base stations to reach certain areas that are adjacent to or even surrounded by a group of base stations. In addition, obstructions from geological features or man-made structures, may simply block signals in certain areas. Base stations may also be considered too expensive to place in lower populated or more rural areas, leaving large areas simply uncovered. Of course, any un-covered area or region means lost revenues for communication system operators or service providers.
Repeaters can provide a cost-effective way for carriers and service providers to fill holes in the coverage area or to augment the area of coverage. For example, rather than install a more expensive and complicated base station, a repeater can be used to extend the reach of existing base stations. Therefore, a carrier can achieve hole filling and otherwise augment the area of coverage for a given sector to provide capacity in an area that was previously not covered. One mark of a hole filling application is that the area is generally surrounded by coverage, often with the very sector that is also in communication with the repeater. Augmenting, or moving, the coverage area of a cell or sector effectively shifts the location or the shape of the coverage area from a sector. An example of this type of application might be to provide highway coverage. Assuming that two sectors cover a highway adjacent to a base station, the use of a repeater might be considered in order to provide coverage to an area beyond that immediately ‘visible’ or reached by signals from the base station location. Especially, for a more rural location.
The use of repeater technology is described in U.S. Pat. No. 6,108,364, entitled “Time Division Duplex Repeater for Use in a CDMA System”, and the use of repeaters for obtaining signal diversity in view of urban canyons is described in U.S. Pat. No. 5,991,345, entitled “Method and Apparatus for Diversity Enhancement Using Pseudo-Multipath Signals”, both of which are incorporated herein by reference.
However, the use of repeaters is not itself without problems in certain situations. As will be discussed further below, a repeater is not a noise-less device and will contribute thermal noise into the base station sector acting as the communication link, referred to as adding to the noise floor of the base station. The use of repeaters is further hindered by environmental factors causing fluctuations in repeater gain, and in the thermal noise contributions by the repeater at the base station. More specifically, the gain provided by a repeater is affected by factors such as: daily temperature variations (±6 dB); seasonal temperature variations (typically ±3 dB); attenuation caused by foliage or foliage changes during spring and summer; or new obstacles being erected along the base station-to-repeater path.
The phenomena stated above will result in fluctuations in the total amount of thermal noise at the base station, adversely affecting coverage as well as service in both the base station and repeater coverage areas. It can be seen that it is desirable to keep the gain of the repeater a constant. Therefore, it is desirable to have the ability to detect and quantify a change, and restore the gain of the repeater back to a pre-determined level.
What is needed is a new apparatus or technique to manipulate the power output of a repeater in such a manner that it can enhance coverage without adding undesirable noise to a communication system. This should be accomplished with a minimum of complexity and maximum ease of use. The present invention satisfies that need.